Variable-pitch color emitting display

ABSTRACT

This disclosure relates to the use of variable-pitch light-emitting devices for display applications, including for displays in augmented reality, virtual reality, and mixed reality environments. In particular, it relates to small (e.g., micron-size) light emitting devices (e.g., micro-LEDs) of variable pitch to provide the advantages, e.g., of compactness, manufacturability, color rendition, as well as computational and power savings. Systems and methods for emitting multiple lights by multiple panels where a pitch of one panel is different than pitch(es) of other panels are disclosed. Each panel may comprise a respective array of light emitters. The multiple lights may be combined by a combiner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/943,568, filed on Dec. 4, 2019, the entire disclosure of which isincorporated herein by reference for all purposes.

FIELD

This disclosure relates in general to systems and methods forvariable-pitch color emitting displays, and in particular to systems andmethods for displays in augmented reality, virtual reality, and mixedreality environments.

BACKGROUND

Some of the current augmented reality (AR) systems and mobile projectiondisplay systems utilize the reflective liquid-crystal on silicon (RLCOS)display, which is a relatively slow-switching device based onliquid-crystal technology, and employs the bulky polarization opticsarchitecture, as exemplified in FIG. 1. Some of the common disadvantagesof this well-established technology are low optical throughput due tothe high losses associated with polarization optical elements and alsolow-speed switching times of 60-120 Hz.

The LCOS projection systems usually consists of a reflective LCOSdisplay and polarization optics with a focusing element, e.g., inFIG. 1. Because of having a front polarizer, at least 55% of light maybe lost immediately and further out-coupled light is lost through thefocusing lens elements. The LC technology, although well-established,cannot change the black-to-color states rapidly and is typically limitedby 120 Hz.

SUMMARY

Systems and methods for emitting multiple lights by multiple panelswhere a pitch of one panel is different than pitch(es) of other panelsare disclosed. Each panel may comprise a respective array of lightemitters. The multiple lights may be combined by a combiner.

In some embodiments, the multiple lights may comprise a red light, agreen light, and a blue light. In some embodiments, each of the multiplelights may be a monochrome light. In some embodiments, light emitters ofone array may be smaller in size than light emitters of other array(s).

In some embodiments, a light emitter of a first array may have a firstsingle-emitter footprint with dimensions associated with a first pitchof a first panel, a light emitter of a second array may have a secondsingle-emitter footprint with dimensions associated with a second pitchof the second panel, a light emitter of a third array may have a thirdsingle-emitter footprint with dimensions associated with a third pitchof a third panel, and the second single-emitter footprint may be smallerthan the first single-emitter footprint and may be smaller than thethird single-emitter footprint.

In some embodiments, a same set of dimensions may be occupied by eachof: the first single-emitter footprint, the third single-emittedfootprint, and a 2×2 array of four light emitters each having the secondsingle-emitter footprint. In some embodiments, a same set of dimensionsmay be occupied by each of: the third single-emitted footprint, a 2×2array of four light emitters each having the first single-emitterfootprint, and a 4×4 array of sixteen light emitters each having thesecond single-emitter footprint.

In some embodiments, a first light may have a first color, a secondlight may have a second color, and a third light may have a third color,and systems may comprise electronic hardware for: receiving video data,performing color-wise down-sampling on the received video data at thefirst color for the first light, performing color-wise down-sampling onthe received video data at the third color for the third light, anddriving the first panel, the second panel, and the third panel, whereinthe first panel is driven based on the color-wise down-sampled videodata at the first color for the first light, and the third panel isdriven based on the color-wise down-sampled video data at the thirdcolor for the third light.

In some embodiments, a first light may have a first color, a secondlight may have a second color, and a third light may have a third color,the systems may comprise first electronic hardware configured for:receiving first video data having a first resolution, and driving thefirst panel based on the first video data having the first resolution;second electronic hardware configured for: receiving second video datahaving a second resolution, and driving the second panel based on thesecond video data having the second resolution; and third electronichardware configured for: receiving third video data having a thirdresolution, and driving the third panel based on the third video datahaving the third resolution, wherein a full-color video is based on thefirst video data, the second video data, and the third video data, andwherein the second resolution for the second panel is higher than thefirst resolution for the first panel and is higher than the thirdresolution for the third panel.

In some embodiments, the combiner may comprise an X-cube combiner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates full-color LCoS-based projector systems employingthree-color illumination and modulation in a parallel fashion.

FIG. 2 illustrates a micro-LED same-pitch X-cube geometry for aprojector system.

FIG. 3 illustrates an exemplary architecture of an individualμLED-emitter.

FIGS. 4A and 4B illustrates example emitter footprints in per-colorvariable resolution scheme, according to embodiments described herein.

FIG. 5 illustrates a representation of a same-pitch micro-LED generatedimage (top) compared to a representation of a variable-pitch micro-LEDgenerated image (bottom).

FIGS. 6A and 6B illustrate example systems each with multiple panels andvarying pitches.

FIGS. 7A-7D illustrate text-based simulation of per-colorvariable-resolution down-sampling.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples that can be practiced. It is tobe understood that other examples can be used and structural changes canbe made without departing from the scope of the disclosed examples.

FIG. 1 illustrates full-color LCoS-based projector systems employingthree-color illumination and modulation in a parallel fashion. On theleft side of FIG. 1, projector system 110 comprises a red-green-blue(RGB) light source 112 (having micro-light-emitting diode (μLED) withmicro-lens array (MLA)), pre-polarization filter 114, polarizationbeamsplitter (PBS) 116, quarter-wave plate (QWP) 118, collimator 120,reflective LCOS display 122, clean-up polarization filter 124,projection lens 126, eyepiece 128 (having input coupler grating (ICG)130 and exit pupil expander (EPE) region 132), and variable focuselement (VFE) 134. The RBG light source 112 provides three-colorillumination and the reflective LCOS display 122 provides modulation ina parallel fashion.

On the right side of FIG. 1, projector system 160 comprises an RGB lightsource 162 (having μLED with MLA), pre-polarization filter 164, PBS 166,QWP 168, reflective LCOS display 172, clean-up polarization filter 174,projection lens 176, eyepiece 178 (having ICG 180 and EPE region 182),and VFE 184. The RBG light source 162 provides three-color illuminationand the reflective LCOS display 172 provides modulation in a parallelfashion.

In FIG. 1, the left-side projector system 110 and the right-sideprojector system 160 differ in various aspects. For example, theleft-side projector system 110 comprises collimator 120, but theright-side projector system 160 has no collimator. As another example,the left-side projector system 110 has an arrangement where QWP 118 islocated in between PBS 116 and collimator 120, but the right-sideprojector system 150 has an arrangement where QWP 168 is located inbetween PBS 166 and reflective LCOS display 172. As yet another example,the left-side projector system 110 has an arrangement where there is noQWP is needed in between PBS 116 and reflective LCOS display 122, butthe right-side projector system 150 has an arrangement where QWP 168 islocated in between PBS 166 and reflective LCOS display 172.

Embodiments described herein may use micro-LED (tiny emittinglight-emitting diode (LED)) devices, which may allow creation of imagesdirectly on the color panel, thus simplifying the optics design,negating polarization optics, and making the use of RLCOS techniquesunnecessary. In addition to the switching speeds of kHz rates, wepropose here (e.g., instead of the commonly employed 3-panelmicro-display architecture of X-cube combiner and projection optics asdepicted in FIG. 2), a novel architecture in which each color panel maybe represented by its own light-emitter pitch and its own resolution.The advantages of such display techniques (e.g., geometry) may includelarge power savings, simplified design, and reduced cost and complexityof the system.

FIG. 2 illustrates a micro-LED same-pitch X-cube geometry for aprojector system. In FIG. 2, projector system 200 comprises a redmicro-LED panel 210, a green micro-LED panel 220, a blue micro-LED panel230, an X-cube combiner 240, projection optics 250, and RBG eyepiece 260(having ICG 270). All three panels 210, 220, and 230 have the same pitchfor their respective micro-LEDs.

A common bottleneck of micro-LED emitting devices, such as those shownin the example of FIG. 3, can be their reduced efficiency with the sizereduction of the individual emitters (e.g., the device pitch and emittersize). For example, 10 um pixel size devices are more efficient than 5um pixel size devices. It can be advantageous (e.g., in terms of opticalemittance) to use larger size emitters. However, that is not alwayspossible when there is a need for high-resolution images and/or adesired field-of-view (FOV).

FIG. 3 illustrates an exemplary architecture of an individualμLED-emitter. In FIG. 3, individual μLED-emitter 300 comprises acomplementary metal-oxide semiconductor (CMOS) backplane 310, a III-Vcompound semiconductor emitter 320, a reflection cup 330, a micro-lens340, and optical insulation 350. The CMOS backplane 310 may usepulse-width modulation (PWM) control for the μLED-emitter 300. The III-Vcompound semiconductor emitter 320 may provide or promote highefficiency for the μLED-emitter 300. The reflection cup 330 may provideor promote high brightness for the μLED-emitter 300. The micro-lens 340may provide or promote light collimation for the μLED-emitter 300. Theoptical insulation 350 may provide or promote display quality for theμLED-emitter 300.

Another problem can lie in utilizing the natural color emitters versuscolor-converted micro-LEDs, especially in the red part of the colorspectrum. A typical approach uses a blue pump LED to pump thesemiconductor stack to color-shift from blue to green and/or redwavelengths. The red emitter uses either a phosphor dye (e.g., foremitters >50 um size emitters), or relies on quantum-dot (QD) colorconversion (e.g., below 50 um size emitters). While these schemes areroutinely utilized, they provide low conversion efficacy rates (e.g.,<30% for blue-red optical conversion), a non-collimated Lambertianoutput, and have limited reliability.

As disclosed herein, using larger size natural red and blue emitters canaddress these problems above. They can improve overall display efficacy(in blue and red panels of blue and red emitters, respectively) whilestill using smaller pixel size green micro-LEDs with very littleapparent degradation of image quality. Embodiments of the disclosuredescribed herein may rely on a simple interesting fact that the humanvision system is best adapted to green light, and therefore the requiredhigh-end resolution for some augmented reality/virtual reality/mixedreality (AR/VR/MR) systems may be reached in green light, but may be notrequired in the red and blue parts of the wavelength spectrum. Thus, onecan still use large size red emitters negating the effect of the lowefficacy in the red wavelengths, which may be particularly important fornot-yet-fully-developed native red micro-LEDs. Since the requiredportion of red (and blue) light can utilize the larger emitters, whichcan produce higher brightness than the solutions with equal-pitch colorpanels, the resulting solutions can offer more opticaloutput/brightness.

Embodiments of the disclosure may employ a novel μLED-based three-color(e.g., R/G/B) projector based on optical combining of light emitted bythree monochrome (e.g., R, G, or B) panels (e.g., via an X-cube colorcombiner). Unlike conventional color projectors based around similaroptical combining schemes, the embodiments described herein may employmultiple (e.g., three) individual monochrome panels havingmicro-emitters with variable pitch per panel.

Some embodiments may employ a projector configuration (e.g., geometry)based around the use of a single (e.g., green) panel having an array of1280×720 emitters with 2.5 μm pitch in conjunction with two (e.g., redand blue) panels each having an array of 640×360 emitters with 5 μmpitch. In such a configuration, the individual monochrome panels mayeach have the same overall dimensions. Due to the variably-pitchedconfiguration, the footprint occupied by a single red pixel and a singleblue pixel may be occupied by four green pixels (e.g., as shown in FIG.4A) after beam-combining.

FIG. 4A illustrates example emitter footprints in per-color variableresolution scheme, according to embodiments described herein. Redemitter footprint 410 may have dimensions of 5 μm×5 μm for a single redpixel. Blue emitter footprint 430 may also have dimensions of 5 μm×5 μmfor a single blue pixel. Green emitter footprint 420 may have dimensionsof 5 μm×5 μm for a 2×2 array of four green pixels, each having a smallerfootprint having dimensions of 2.5 μm×2.5 μm for a single green pixel.

Another example configuration may employ a green panel having an arrayof 1280×720 emitters with 2.5 μm pitch, a red panel having an array of640×360 emitters with 5 μm pitch, and a blue panel having an array of320×180 emitters with 10 μm pitch. In this configuration, the footprintoccupied by a single blue pixel may be occupied by four red pixels andsixteen green pixels (e.g., as shown in FIG. 4B).

FIG. 4B illustrates example emitter footprints in per-color variableresolution scheme, according to embodiments described herein. Redemitter footprint 450 may have dimensions of 10 μm×10 μm for a 2×2 arrayof four red pixels, each having a smaller footprint having dimensions of5 μm×5 μm for a single red pixel. Blue emitter footprint 430 may havedimensions of 10 μm×10 μm for a single blue pixel. Green emitterfootprint 420 may have dimensions of 10 μm×10 μm for a 4×4 array ofsixteen green pixels, each having a smaller footprint having dimensionsof 2.5 μm×2.5 μm for a single green pixel.

Both of these above example architectures may take advantage of theaforementioned characteristics of the human visual system, in whichacuity may be most prevalent for green wavelengths and least so for bluewavelengths.

Employing embodiments of the disclosure, full-color computer imagery maybe presented at full resolution (e.g., 1280×720) in the green channeland at quarter-resolution (e.g., 640×360) for the red and blue channels,or even lower resolution for the blue channel. In an example hardwareinstantiation, one of two video data processing and transmission schemescan be used: 1) full-resolution, full-color imagery can be presented tocombined electronic hardware responsible for driving all three μLEDpanels, at which point the color-wise down sampling for thelower-resolution color panels can occurs at the hardware level, or 2)imagery per color can be rendered at different resolutions (e.g., greenat 1280×720, red at 640×360, blue at 640×360 or less) and transmitted toindividual driving electronic hardware per panel in parallel datastreams.

Embodiments can remove the need for the small-size emitters (e.g., 2.5um or so) required for high-resolution optical systems of <2 arc min forlarge fields of view (FOVs). For example, it is demonstrated that usingBlue-panel and Red-panel color pixels that are twice the size ofemitters for Green-panel is viable. This concept can remove a principalsource of uncertainty for uLED displays, which was the red intensity fornative (not color-converted) red sources. It can also help with theBlue-panel which apparently can also be difficult to scale down towards2.5 um pixel size devices. Again, using the large size Blue and Redpanels can give brighter displays, and can reduce power consumption (assmaller size emitters can become less efficient due to a higher currentdensity and semiconductor edge effect), while use of a higher-pitchgreen panel can provide the appropriate level of image quality for humanperception. Moreover, maintaining the same overall format can allow oneto keep the same projection system as a common standard.

FIG. 5 illustrates a representation of a same-pitch micro-LED generatedimage (top) compared to a representation of a variable-pitch micro-LEDgenerated image (bottom). The bottom image 520 represents an imagegenerated using blue and red emitters that are twice as large comparedto the green emitter. The image quality for both the top image 510 andthe bottom image 520 can appear to the human visual system to be nearlyidentical.

FIGS. 6A and 6B illustrate example systems each with multiple panels andvarying pitches. In FIGS. 6A and 6B, system 602 and system 604 may eachcomprise a first panel 610, a second panel 620, a third panel 630, anX-cube combiner 640, and projection optics 650. One or more of the redpanel 610, the green LED panel 620, and blue LED panel 630 may comprisea micro-LED panel. One or more of the red panel 610, the green LED panel620, and blue LED panel 630 may comprise a monochrome light panel. Thethree panels 610, 620, and 630 may have a respective pitch for theirrespective light-emitting elements, and the three respective pitches maybe non-uniform, as described in the examples and embodiments above.System 602 and system 604 may each be used with an eyepiece 660, such asfor an AR or VR or MR system. In FIG. 6A, system 602 may be used withcombined electronic hardware 670 (e.g., combined driving circuitry) fordriving all three panels 610, 620, and 630, as described above for afirst example hardware instantiation for a first video data processingand transmission scheme. In FIG. 6B, system 604 may be used with threeseparate individual pieces 615, 625, and 635 of electronic hardware(e.g., three separate driving circuits) for driving the three panels610, 620, and 630, respectively, as described above for a second examplehardware instantiation for a second video data processing andtransmission scheme.

Systems 602 and 604 of FIGS. 6A and 6B may each create or generateimages directly on one or more of first panel 610, second panel 620, andthird panel 630. Compared with other display system designs, systems 602and 604 may each have a simplified optics design. For example,polarization optics may be reduced or negated, so that each of systems602 and 604 may exclude or lack any or all of the polarizationcomponents in FIG. 1. As another example, an LCOS display may beunnecessary, so that each of systems 602 and 604 may exclude or lack anyor all LCOS displays in FIG. 1. Systems 602 and 604 may each operate atkHz switching speeds. Compared with other display system designs,systems 602 and 604 may each provide large power savings. Compared withother display system designs, systems 602 and 604 may each providereduced cost or complexity.

FIGS. 7A-7D illustrate text-based simulation of per-colorvariable-resolution down-sampling. FIG. 7A represents full-resolutionrendering 710 for red, green, and blue color channels. FIG. 7Brepresents full-resolution rendering 720 for green andquarter-resolution down-sampling and rendering for red and blue. FIG. 7Crepresents full-resolution rendering 730 for green, quarter-resolutiondown-sampling for red, and sixteenth-resolution down-sampling for blue.FIG. 7D represents quarter-resolution rendering 740 for red, green, andblue color channels.

Among these four renderings, rendering 710 may appear to the humanvisual system to have the highest color contrast (e.g., letter coloringvs. background coloring) and the highest sharpness (e.g., edges ofletters). Renderings 720 and 730 may appear to the human visual systemto be nearly identical. Rendering 710 may appear to the human visualsystem to have solid white lettering. Relative to rendering 710, thelettering of renderings 720 and 730 may appear to have a faint greentinge. Rendering 730 may appear to the human visual system to have asimilar white color for its lettering, but the sharpness may appear tobe the lowest among all four renderings depicted by FIGS. 7A-7D.

Although the disclosed examples have been fully described with referenceto the accompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Forexample, elements of one or more implementations may be combined,deleted, modified, or supplemented to form further implementations. Suchchanges and modifications are to be understood as being included withinthe scope of the disclosed examples as defined by the appended claims.

What is claimed is:
 1. A system comprising: a first panel comprising a first array of light emitters, the first panel configured for emitting a first light at a first pitch; a second panel comprising a second array of light emitters, the second panel configured for emitting a second light at a second pitch; a third panel comprising a third array of light emitters, the third panel configured for emitting a third light at a third pitch; and a combiner for combining the first light, the second light, and the third light, wherein the second pitch of the second panel is smaller than the first pitch of the first panel and is smaller than the third pitch of the third panel.
 2. The system of claim 1, wherein the first light comprises a red light, the second light comprises a green light, and the third light comprise a blue light.
 3. The system of claim 2, wherein each of the first light, the second light, and the third light is a monochrome light.
 4. The system of claim 1, wherein the light emitters of the first array are smaller in size than the light emitters of the second array and are smaller in size than the light emitters of the third array.
 5. The system of claim 1, wherein: a light emitter of the first array has a first single-emitter footprint with dimensions associated with the first pitch of the first panel, a light emitter of the second array has a second single-emitter footprint with dimensions associated with the second pitch of the second panel, a light emitter of the third array has a third single-emitter footprint with dimensions associated with the third pitch of the third panel, and the second single-emitter footprint is smaller than the first single-emitter footprint and is smaller than the third single-emitter footprint.
 6. The system of claim 5, wherein a same set of dimensions is occupied by each of: the first single-emitter footprint, the third single-emitted footprint, and a 2×2 array of four light emitters each having the second single-emitter footprint.
 7. The system of claim 5, wherein a same set of dimensions is occupied by each of: the third single-emitted footprint, a 2×2 array of four light emitters each having the first single-emitter footprint, and a 4×4 array of sixteen light emitters each having the second single-emitter footprint.
 8. The system of claim 1, wherein the first light has a first color, the second light has a second color, and the third light has a third color, the system comprising: electronic hardware configured for: receiving video data, performing color-wise down-sampling on the received video data at the first color for the first light, performing color-wise down-sampling on the received video data at the third color for the third light, and driving the first panel, the second panel, and the third panel, wherein the first panel is driven based on the color-wise down-sampled video data at the first color for the first light, and the third panel is driven based on the color-wise down-sampled video data at the third color for the third light.
 9. The system of claim 1, wherein the first light has a first color, the second light has a second color, and the third light has a third color, the system comprising: first electronic hardware configured for: receiving first video data having a first resolution, and driving the first panel based on the first video data having the first resolution; second electronic hardware configured for: receiving second video data having a second resolution, and driving the second panel based on the second video data having the second resolution; and third electronic hardware configured for: receiving third video data having a third resolution, and driving the third panel based on the third video data having the third resolution, wherein a full-color video is based on the first video data, the second video data, and the third video data, and wherein the second resolution for the second panel is higher than the first resolution for the first panel and is higher than the third resolution for the third panel.
 10. The system of claim 1, wherein the combiner comprises an X-cube combiner.
 11. A method comprising: emitting, by a first panel comprising a first array of light emitters, a first light at a first pitch; emitting, by a second panel comprising a second array of light emitters, a second light at a second pitch; emitting, by a third panel comprising a third array of light emitters, a third light at a third pitch; and combining, by a combiner, the first light, the second light, and the third light, wherein the second pitch of the second panel is smaller than the first pitch of the first panel and is smaller than the third pitch of the third panel.
 12. The method of claim 11, wherein the first light comprises a red light, the second light comprises a green light, and the third light comprise a blue light.
 13. The method of claim 12, wherein each of the first light, the second light, and the third light is a monochrome light.
 14. The method of claim 11, wherein the light emitters of the first array are smaller in size than the light emitters of the second array and are smaller in size than the light emitters of the third array.
 15. The method of claim 11, wherein: a light emitter of the first array has a first single-emitter footprint with dimensions associated with the first pitch of the first panel, a light emitter of the second array has a second single-emitter footprint with dimensions associated with the second pitch of the second panel, a light emitter of the third array has a third single-emitter footprint with dimensions associated with the third pitch of the third panel, and the second single-emitter footprint is smaller than the first single-emitter footprint and is smaller than the third single-emitter footprint.
 16. The method of claim 15, wherein a same set of dimensions is occupied by each of: the first single-emitter footprint, the third single-emitted footprint, and a 2×2 array of four light emitters each having the second single-emitter footprint.
 17. The method of claim 15, wherein a same set of dimensions is occupied by each of: the third single-emitted footprint, a 2×2 array of four light emitters each having the first single-emitter footprint, and a 4×4 array of sixteen light emitters each having the second single-emitter footprint.
 18. The method of claim 11, wherein the first light has a first color, the second light has a second color, and the third light has a third color, the method comprising: receiving video data, performing color-wise down-sampling on the received video data at the first color for the first light, performing color-wise down-sampling on the received video data at the third color for the third light, and driving the first panel, the second panel, and the third panel, wherein the first panel is driven based on the color-wise down-sampled video data at the first color for the first light, and the third panel is driven based on the color-wise down-sampled video data at the third color for the third light.
 19. The method of claim 11, wherein the first light has a first color, the second light has a second color, and the third light has a third color, the method comprising: receiving first video data having a first resolution; driving the first panel based on the first video data having the first resolution; receiving second video data having a second resolution; driving the second panel based on the second video data having the second resolution; receiving third video data having a third resolution; and driving the third panel based on the third video data having the third resolution, wherein a full-color video is based on the first video data, the second video data, and the third video data, and wherein the second resolution for the second panel is higher than the first resolution for the first panel and is higher than the third resolution for the third panel.
 20. The method of claim 11, wherein the combiner comprises an X-cube combiner. 